Conventionally, in order to obtain a laminated board, and an electronic component such as a printed wiring board, various resin compositions have been used. For example, in a multilayer printed wiring board, in order to form an insulating layer for insulating between inside layers or to form an insulating layer positioned in a surface layer part, a resin composition is used. On a surface of the insulating layer, a wiring that is generally a metal is laminated. Further, in order to form an insulating layer, a B-stage film in which the above-described resin composition is formed into a film may be used in some cases. The resin composition and the B-stage film are used for an insulating material for a printed wiring board including a build-up film.
As an example of the above-described resin composition, in the following Patent Document 1, a resin composition containing a polyfunctional epoxy resin (with the proviso that a phenoxy resin is excluded) (A), a phenolic curing agent and/or an active ester-based curing agent (B), a thermoplastic resin (C), an inorganic filler (D), and a quaternary phosphonium-based curing accelerator (E) have been disclosed. As the thermoplastic resin (C), a thermoplastic resin selected from a phenoxy resin, a polyvinylacetal resin, a polyimide, a polyamideimide resin, a polyethersulfone resin, and a polysulfone resin can be mentioned. As the quaternary phosphonium-based curing accelerator (E), one kind or more of quaternary phosphonium-based curing accelerators selected from tetrabutylphosphonium decanoate, (4-methylphenyl)triphenylphosphonium thiocyanate, tetraphenylphosphonium thiocyanate, and butyl triphenylphosphonium thiocyanate can be mentioned.